The Large-Scale Climate in Response to the Retreat of the West Antarctic Ice Sheet

Abstract

ased upon coupled climate simulations driven by present-day conditions and conditions resembling the Marine Isotope Stage 31 (this simulation is called WICE-EXP), insofar as the West Antarctic Ice Sheet (WAIS) configuration is concerned, it is demonstrated that changes in the WAIS orography lead to noticeable changes in the oceanic and atmospheric circulations. Compared with the present-day climate, WICE-EXP is characterized by warmer conditions in the Southern Hemisphere (SH) by up to 5°C in the polar oceans and up to 2°C in the Northern Hemisphere (NH). These changes feed back on the atmospheric circulation weakening (strengthening) the extratropical westerlies in the SH (northern Atlantic). Calculations of the southern annular mode (SAM) show that modification of the WAIS induces warmer conditions and a northward shift of the westerly flow; in particular, there is a clear weakening of the polar jet. These changes lead to modification of the rate of deep water formation, reducing the magnitude of the North Atlantic Deep Water but enhancing the Antarctic Bottom Water. By evaluating the density flux it is found that the thermal density flux has played a main role in the modification of the meridional overturning circulation. Moreover, the climate anomalies between the WICE-EXP and the present-day simulations resemble a bipolar seesaw pattern. These results are in good agreement with paleorecontructions in the framework of the Ocean Drilling Program and Antarctic Geological Drilling (ANDRILL) project.